The present invention relates to a lens combination for protective eyewear for industrial workers, the lens arrangements reducing or eliminating the transmission of eye-damaging wavelengths to the wearer, thus preventing impairment of the vision of the lens wearer while facilitating visualization of work, particularly in certain industrial settings.
The ill effects to the human eye due to the absorption of radiation emitted by artificial light sources has received increasing attention. Optical effects can be particularly detrimental to industrial workers in vocations such as welding or glass-blowing, where visual exposure to damaging radiation may be intensified. Acute exposure is believed to result in corneal and/or retinal burns, while chronic exposure may produce corneal or lenticular opacities (cataracts).
General tissue damage to various parts of the eye has resulted from exposure to varying wavelengths across the entire spectrum. Retinal damage is possible in the visible and near infrared range (400 to 1400 nanomenters). Due to the focusing effects of the cornea and lens, the incident corneal radiant exposure at the retina will be increased by about 100,000 times.
Light in the ultraviolet (UV) and far infrared (IR) spectra produces harmful ocular effects principally at the cornea, although radiation at certain wavelengths may reach the lens and cause damage to that structure.
Actinic UV radiation at short wavelengths in the range of from 200 to 315 nanometers is responsible for what has been termed xe2x80x9cwelders flashxe2x80x9d or photokeratitis. These are also the wavelengths responsible for sunburn in humans. Near UV radiation between 315 and 400 nanometers is particularly absorbed in the lens and may contribute to some forms of cataract.
Middle IR, between 1400 and 3000 nanometers, penetrates more deeply into the eye, and may contribute significantly to what has been termed xe2x80x9cglass blower""s cataractxe2x80x9d. Extensive exposure to near IR may also contribute to such cataracts.
Radiation at visible (400 to 780 nanometers) and near IR (780 to 1400 nanometers) is transmitted through the ocular media with little loss and usually is focused on a spot on the retina 10 to 20 microns in diameter. Such focusing may create intensities high enough to damage the retina. Wavelengths between 400 and 550 nanometers become particularly hazardous over long-term retinal exposures lasting for minutes or hours. This is often referred to as xe2x80x9cblue light hazard.xe2x80x9d
In the past, an assortment of optical filtering devices have been developed in an attempt to provide protection for the human eye from exposure to potentially damaging radiation at varying wavelengths. Matsushita (U.S. Pat. No. 5,922,246) describes a didymium-like organic dye in a compound which is compatible with a resin base material, resulting in a protective optical device that has a transmittance of not less 15% over the 590 to 660 nanometer range. U.S. Pat. No. 5,949,518 discloses a device with a polymer matrix, dye, and UV absorber coating, which absorbs in the 290 to 380 nanometer range.
The Gallas Patent 4,698,374 shows a photochromic lens system in which a layer of melanin pigment functions as an absorbent across the broad spectrum of UV, visible, and near IR wavelengths. U.S. Pat. No. 4,320,939 discloses a light-filtering optical system in which the filter element contains stable fluorescent dyes such as oxazine, carbazine, and carbopyronin. This combination absorbs across a wide variation from about 10% to about 99%, in a wavelength range of about 400 to 700 nanometers.
While these optical systems may all provide adequate eye protection for a specific use at varying ranges of wavelengths, there exists a need for a lens that significantly reduces or eliminates the transmission of the most damaging wavelengths, particularly in ranges between 570 and 610 nanometers.
The present invention consists of industrial protective eyewear lens combinations which significantly reduce or eliminate the transmission of certain eye-damaging ultraviolet and infrared radiation. As a result, the vision of the lens wearer is not impaired, and the wearer is able to more readily visualize his or her work while specific troublesome wavelengths are being filtered out.
It is therefore an object of the present invention to provide a protective eyewear lens system which prevents transmission of virtually all damaging radiation, particularly in a wavelength range of about 570 to 610 nanometers.
It is a further object of the present invention to provide a protective eyewear lens system which prevents transmission of at least 80% of damaging radiation, particularly in a wavelength range of 480 to 550 nanometers.